Pollution leaves us heart-broken

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The WHO rate bad air quality as one of the leading causes of heart attacks and strokes worldwide. It's also known that people who lay asphalt have a much higher rate of heart disease. David Newby, at the University of Edinburgh, explained to Chris Smith how he is investigating why this is.

Chris - But it's not just fish that are exposed to oil-based pollution: bad air quality is now considered to be one of the leading causes of heart attacks and strokes worldwide. Dave Newby, at the University of Edinburgh, has been investigating how...

Dave - My name's Dave Newby, I'm a British Heart Foundation John Wheatley Chair of Cardiology at the University of Edinburgh.

People have observed for quite a while that high air pollution has bad health effects and that's been known since the mid-1900s. What people have appreciated more recently is that beyond the obvious that air pollution can make your breathing bad, it actually increases the risk of heart attacks and strokes. So that's where I start to become interested because of this association of air pollution and you having heart attacks and heart disease. And not only getting it over time but also there's evidence that it actually triggers a heart attack.

Chris - This isn't just because people who are struggling to breathe that's just a stressful situation and that makes them have a heart attack - there's something more going on?

Dave - That's right, yes. It's more than that because the pollution that's in the air is actually sometimes imperceptible . The particles in the air are so small you can hardly see them, so it's not that. People keep asking well, what's the mechanism of that? OK, you see the association but it doesn't make sense to me. So what we did we set off on a programme of work to look at the mechanisms of how air pollution can do this and it was in many ways quite intriguing. So what we did was we worked with some investigators in Sweden. We went there because they have a unique exposure chamber and they have, of course, a Volvo engine. So what we did we had this diesel Volvo engine and we diluted down the exhaust and then fed it into this chamber which, of course, did raise some eyebrows I have to say.

Chris - Hang on a minute! You put people in a chamber and you blow in car exhaust for them to breathe?

Dave - Absolutely.

Chris - How did you get that through an ethics committee?

Dave - That's exactly what the British Heart Foundation said to me. And what was quite interesting was when I pointed out to them the levels inside this chamber were lower than the levels outside their front door because, at that time, they were in a very, very polluted area of London which was absolutely the highest levels in London recorded just round the corner. So I said to them if it's ethical for them to invite me down from Edinburgh to London to their polluted city and go on their committee, then it's ethical for me to do that. And it was diluted of course so the levels that we have are the levels you would expect at the roadside of a busy road and so this was relevant to what we see in the cities.

We got people to exercise gently in those chambers to breathe in this and then we looked at how their blood vessels responded. Now what we found was that the blood vessels were more tight and more constricted, they didn't relax as much, and the blood that flowed through it was much more sticky, and much more likely to cause blood clots. And those two things together, blood vessels that aren't relaxing, that are tight and have blood clots are just the recipe for heart attacks and strokes.

Chris - Do you know what component it was in the smoke that was doing that?

Dave - Yes. So in the exhaust, there are various different things. There are gases but there are also these particles. They are really tiny particles so they are so small you cannot see them by the naked eye. They are what we call nanoparticles - really tiny. It seemed to be those particles and they're covered in bits of metal, bits of unburned fuel, organic components, metals, and these things can react quite nastily to biological tissues, and what we were able to show was that it seems to be these tiny microscopic particles are what seemed to be causing the problem.

Chris - Just because you breathe them in or do they go further afield in you body once you breathe in?

Dave - Yes, that's a very important question and, actually, if I'm truly honest we don't really know for certain but there are three potential mechanisms. One - it goes into the lung, the lung doesn't like it and sends out messages to the rest of the body. Another mechanism is that they go deep into the lung, they get gobbled up by the cells of the body (the immune cells), and then they go into the bloodstream, and there they might harm the blood vessels, or they could even go straight into the bloodstream. We have some some preliminary data that these particles are so tiny, so small that they can cross cell membranes and get into the bloodstream. There they might actually cause the furring up of the blood vessels and cause heart attacks and strokes.

Chris - What about actually monitoring the real life experience of people in real life situation to see what their exposure is. Can we do that - do we have that sort of data?

Dave - We do. We can use personal monitoring so you wear this lovely backpack which monitors the quality of the air. It measures the particles, the mass, the number of particles, the gases in the air, and so you've got like a portable laboratory on your back. And we walked around Beijing just before the Olympic Games and we were able to see the quite dramatic levels of air pollution there.

We actually then went on to do a study where we got patients to wear a face mask. It's an industrial mask, this is not the simple cloths that you see people put in front of their faces. But this is a mask that's very efficient, takes out a lot of these particles and when we got people to walk round just for one day with these masks on, their blood pressure was lower, their breathing was easier, and some of the measures that we did of how much heart stress they were under were much lower. So actually stopping breathing in some of these particles in the air around you does seem to have benefits for the body.